function AlignmentPattern(posX, posY, estimatedModuleSize) {
	this.x = posX;
	this.y = posY;
	this.count = 1;
	this.estimatedModuleSize = estimatedModuleSize;

	this.__defineGetter__("EstimatedModuleSize", function () {
		return this.estimatedModuleSize;
	});
	this.__defineGetter__("Count", function () {
		return this.count;
	});
	this.__defineGetter__("X", function () {
		return Math.floor(this.x);
	});
	this.__defineGetter__("Y", function () {
		return Math.floor(this.y);
	});
	this.incrementCount = function () {
		this.count++;
	}
	this.aboutEquals = function (moduleSize, i, j) {
		if (Math.abs(i - this.y) <= moduleSize && Math.abs(j - this.x) <= moduleSize) {
			var moduleSizeDiff = Math.abs(moduleSize - this.estimatedModuleSize);
			return moduleSizeDiff <= 1.0 || moduleSizeDiff / this.estimatedModuleSize <= 1.0;
		}
		return false;
	}

}

function AlignmentPatternFinder(image, startX, startY, width, height, moduleSize, resultPointCallback) {
	this.image = image;
	this.possibleCenters = new Array();
	this.startX = startX;
	this.startY = startY;
	this.width = width;
	this.height = height;
	this.moduleSize = moduleSize;
	this.crossCheckStateCount = new Array(0, 0, 0);
	this.resultPointCallback = resultPointCallback;

	this.centerFromEnd = function (stateCount, end) {
		return (end - stateCount[2]) - stateCount[1] / 2.0;
	}
	this.foundPatternCross = function (stateCount) {
		var moduleSize = this.moduleSize;
		var maxVariance = moduleSize / 2.0;
		for (var i = 0; i < 3; i++) {
			if (Math.abs(moduleSize - stateCount[i]) >= maxVariance) {
				return false;
			}
		}
		return true;
	}

	this.crossCheckVertical = function (startI, centerJ, maxCount, originalStateCountTotal) {
		var image = this.image;

		var maxI = image.height;
		var stateCount = this.crossCheckStateCount;
		stateCount[0] = 0;
		stateCount[1] = 0;
		stateCount[2] = 0;

		// Start counting up from center
		var i = startI;
		while (i >= 0 && image.data[centerJ + i * image.width] && stateCount[1] <= maxCount) {
			stateCount[1]++;
			i--;
		}
		// If already too many modules in this state or ran off the edge:
		if (i < 0 || stateCount[1] > maxCount) {
			return NaN;
		}
		while (i >= 0 && !image.data[centerJ + i * image.width] && stateCount[0] <= maxCount) {
			stateCount[0]++;
			i--;
		}
		if (stateCount[0] > maxCount) {
			return NaN;
		}

		// Now also count down from center
		i = startI + 1;
		while (i < maxI && image.data[centerJ + i * image.width] && stateCount[1] <= maxCount) {
			stateCount[1]++;
			i++;
		}
		if (i == maxI || stateCount[1] > maxCount) {
			return NaN;
		}
		while (i < maxI && !image.data[centerJ + i * image.width] && stateCount[2] <= maxCount) {
			stateCount[2]++;
			i++;
		}
		if (stateCount[2] > maxCount) {
			return NaN;
		}

		var stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
		if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal) {
			return NaN;
		}

		return this.foundPatternCross(stateCount) ? this.centerFromEnd(stateCount, i) : NaN;
	}

	this.handlePossibleCenter = function (stateCount, i, j) {
		var stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
		var centerJ = this.centerFromEnd(stateCount, j);
		var centerI = this.crossCheckVertical(i, Math.floor(centerJ), 2 * stateCount[1], stateCountTotal);
		if (!isNaN(centerI)) {
			var estimatedModuleSize = (stateCount[0] + stateCount[1] + stateCount[2]) / 3.0;
			var max = this.possibleCenters.length;
			for (var index = 0; index < max; index++) {
				var center = this.possibleCenters[index];
				// Look for about the same center and module size:
				if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {
					return new AlignmentPattern(centerJ, centerI, estimatedModuleSize);
				}
			}
			// Hadn't found this before; save it
			var point = new AlignmentPattern(centerJ, centerI, estimatedModuleSize);
			this.possibleCenters.push(point);
			if (this.resultPointCallback != null) {
				this.resultPointCallback.foundPossibleResultPoint(point);
			}
		}
		return null;
	}

	this.find = function () {
		var startX = this.startX;
		var height = this.height;
		var maxJ = startX + width;
		var middleI = startY + (height >> 1);
		// We are looking for black/white/black modules in 1:1:1 ratio;
		// this tracks the number of black/white/black modules seen so far
		var stateCount = new Array(0, 0, 0);
		for (var iGen = 0; iGen < height; iGen++) {
			// Search from middle outwards
			var i = middleI + ((iGen & 0x01) == 0 ? ((iGen + 1) >> 1) :  - ((iGen + 1) >> 1));
			stateCount[0] = 0;
			stateCount[1] = 0;
			stateCount[2] = 0;
			var j = startX;
			// Burn off leading white pixels before anything else; if we start in the middle of
			// a white run, it doesn't make sense to count its length, since we don't know if the
			// white run continued to the left of the start point
			while (j < maxJ && !image.data[j + image.width * i]) {
				j++;
			}
			var currentState = 0;
			while (j < maxJ) {
				if (image.data[j + i * image.width]) {
					// Black pixel
					if (currentState == 1) {
						// Counting black pixels
						stateCount[currentState]++;
					} else {
						// Counting white pixels
						if (currentState == 2) {
							// A winner?
							if (this.foundPatternCross(stateCount)) {
								// Yes
								var confirmed = this.handlePossibleCenter(stateCount, i, j);
								if (confirmed != null) {
									return confirmed;
								}
							}
							stateCount[0] = stateCount[2];
							stateCount[1] = 1;
							stateCount[2] = 0;
							currentState = 1;
						} else {
							stateCount[++currentState]++;
						}
					}
				} else {
					// White pixel
					if (currentState == 1) {
						// Counting black pixels
						currentState++;
					}
					stateCount[currentState]++;
				}
				j++;
			}
			if (this.foundPatternCross(stateCount)) {
				var confirmed = this.handlePossibleCenter(stateCount, i, maxJ);
				if (confirmed != null) {
					return confirmed;
				}
			}
		}

		// Hmm, nothing we saw was observed and confirmed twice. If we had
		// any guess at all, return it.
		if (!(this.possibleCenters.length == 0)) {
			return this.possibleCenters[0];
		}

		throw "Couldn't find enough alignment patterns";
	}

}

export default
AlignmentPatternFinder
